Earth-moving machines, such as hydraulic excavators and backhoes, are commonly used to move and excavate earth and other materials. Such machines typically include a chassis, a boom rotatably and pivotably coupled to the chassis, an arm or dipper stick pivotably coupled to the boom and a bucket pivotably coupled to the dipper stick. To pivot the bucket relative to the dipper stick, the dipper stick additionally supports a bucket pivot actuation linkage composed of a plurality of links coupled at one end to the dipper stick and coupled at another end to the bucket. The bucket pivot actuation links are pivoted relative to one another by a hydraulic cylinder assembly to thereby pivot the bucket about a main pivot axis. Pivotal movement of the bucket by the hydraulic cylinder assembly creates a digging or break out force. This digging force is generally defined as the force generated by the hydraulic cylinder assembly tangent to the arc or radius extending from the main pivot axis to the tip of the bucket's working edge or teeth. See S.A.E. Standard J1179, dated February 1990.
In many circumstances, it is necessary to replace an existing bucket on the earth-moving machine with a different bucket. Once the existing bucket has been removed, the new bucket must be mounted to the dipper stick. In conventional backhoes, this is achieved by aligning apertures formed in the bucket with apertures formed in an end of the dipper stick and by manually inserting a pin through these openings. Although seemingly simple, this procedure is tedious and time consuming for several reasons. First, the openings must be in precise alignment to enable the pin to be manually inserted with minimal force by the operator. However, perfectly aligning the apertures may require several attempts. Second, even assuming that the operator is able to perfectly align the apertures with a single attempt, the operator still must exit the operator station of the backhoe to manually insert the pin.
As a result of such difficulties, a multitude of bucket attachment devices have been developed which provide remote controlled extendable and retractable pins for coupling the bucket to the dipper stick and the bucket pivot actuation linkage. Despite eliminating the need for the operator to manually insert a pin to couple the bucket to the dipper stick, such attachment devices have several associated drawbacks. First, such attachment devices typically utilize a space consuming actuator to extend and retract the pins. In particular, one such known device utilizes a pair of hydraulic cylinders mounted about the pins to extend and retract the pins. Utilizing such a space consuming actuator is difficult due to the generally limited amount of space available at the junction of the bucket and the dipper stick.
Second, such prior bucket attachment devices typically offset the bucket pivot axes from the points at which the bucket is releasably connected to the dipper stick and the bucket pivot actuation linkage. For example, in one known bucket attachment device, the bucket pivots about first and second spaced-apart axes, yet is releasably connected to the dipper stick and the bucket pivot actuation linkage along third and fourth distinct axes. Due to this offset, the arc defined by the radius extending from the main bucket pivot axis to the tip of the working edge of the bucket is increased. As a result, the digging force generated by the bucket cylinders is reduced.
Thus, there is a continuing need for a hydraulic excavator and backhoe bucket attachment device or coupler which can be remotely controlled, which requires a minimum amount of space so as to be positioned in the limited space between the dipper stick and the bucket, and which does not reduce the digging force of the bucket by offsetting the bucket attachment points from the bucket pivot axes.